The purpose of this study is to quantify geochemical reactions of CO₂ and brine with subsurface samples taken from the Mt. Simon sandstone and identify any potential alterations of the geomechanical rock properties that could lead to changes observable in seismic monitoring or result in changes of micro seismicity such as those observed at the Illinois Basin-Decatur Project (IBDP) site. Two Mt. Simon sandstone samples from 6919.3 feet (2109.0 m) and 6926.1 feet (2111.1 m) depth were exposed to supercritical CO₂ (scCO₂) dissolved in brine at in-situ reservoir conditions for one month. Geochemical, spectral, scanning electron microscopy, and petrophysical methods were used to analyze the samples before and after the one-month exposure. Significant changes were observed. Multiple geomechanical properties were chosen to form the framework against which to interrogate the petrophysical data: Young’s modulus (E), Poisson’s ratio (ν), lambda·rho (λρ), and mu·rho (μρ). In this study we conclude that framework composition, porosity, heterogeneities, effective pressure, and reactive geochemistry are first order controls on trends in the E-μ and λρ-μρ cross plot spaces. Changes in porosity, permeability, dynamic moduli, and brittleness with exposure to these fluids were observed. No change in ultrasonic P-wave attenuation (Q_P) was observed. Geochemical alteration causes a distinct shift in λρ-μρ in both samples as well as changes in E, ν , and P and S wave seismic velocity values. These observations could provide insight into subsurface monitoring using seismic methods including amplitude variation with offset (AVO) classification.

这项研究的目的是量化CO ₂和盐水与取自Mt的地下样品的地球化学反应。西蒙砂岩，并确定地质力学岩石特性的任何潜在变化，这些变化可能导致地震监测中观察到的变化或导致微地震活动性的变化，例如在伊利诺伊斯盆地-迪凯特项目（IBDP）现场观测到的变化。两山 从6919.3英尺（2109.0米）和6926.1英尺（2111.1米）深度西蒙砂岩样品暴露于超临界二氧化碳₂（SCCO ₂溶解在盐水）在原位水库条件为一个月。在暴露一个月之前和之后，使用地球化学，光谱，扫描电子显微镜和岩石物理方法对样品进行分析。观察到显着变化。选择了多种地质力学特性以形成可查询岩石物理数据的框架：杨氏模量（E），泊松比（ν），λ·rho（λρ）和mu·rho（μρ）。在这项研究中，我们得出结论，构架组成，孔隙度，非均质性，有效压力和反应地球化学是E-μ和λρ-μρ交会图空间趋势的一阶控制。观察到这些流体暴露后孔隙率，渗透率，动态模量和脆性的变化。超声波P波衰减（Q _P） 被观测到。地球化学变化导致两个样本中λρ-μρ的明显偏移，以及E，ν 以及P和S波地震速度值的变化。这些观察结果可以提供对使用地震方法进行地下监测的见识，包括带偏移量的振幅变化（AVO）分类。